Catalysts and Enzymes Notes

Catalysts

  • Catalysts accelerate chemical reactions.
  • They achieve this by reducing the activation energy required for the reaction.
  • A lower activation energy means less energy is needed to initiate the reaction, resulting in a faster reaction rate.
  • The catalyst itself remains unchanged throughout the reaction.
  • The catalyst does not alter the initial and final energy levels of the reactants and products.

Activation Energy

  • Catalysts function by lowering the activation energy.
  • Analogy: Pushing a rock over a hill requires energy; a lower hill makes the task easier.
  • Reactions need sufficient energy (activation energy) to occur rapidly.
  • Catalysts reduce the "height of the hill," or the activation energy, speeding up reactions.

Energy of Life

  • Life depends on energy intake, transformation, and release through chemical reactions.
  • These reactions must occur quickly in living organisms.

Enzymes as Biological Catalysts

  • Enzymes are catalysts produced by living organisms.
  • They are almost always proteins.
  • Enzymes expedite chemical reactions within living cells.
  • Enzymes function by reducing activation energies.

How Enzymes Work

  • Enzymes accelerate reactions by decreasing the activation energy required.
  • The energy of the reactants and products remains constant, but the activation energy is reduced by the enzyme.

Naming Enzymes

  • Many enzymes have names ending in "-ase."
  • Examples: lactase, amylase, and peptidase.

Common Enzymes: Lactase

  • Lactase aids in the digestion of dairy products.
  • Lactose, a disaccharide found in dairy, is broken down by lactase into two monosaccharides.

Common Enzymes: Lactose Intolerance

  • Lactose intolerance arises from the body's inability to produce lactase in adulthood.
  • Lactaid pills containing lactase can be taken to aid in digesting dairy.

Common Enzymes: Amylase

  • Amylase, present in human saliva, initiates carbohydrate digestion in the mouth.
  • Amylase breaks down starch into maltose (a disaccharide) through chewing.

Common Enzymes: Amylase and Starch Digestion

  • Potatoes contain starch, which is composed of numerous bound sugar molecules.
  • Amylase breaks down starch into smaller sugar molecules (maltose) during chewing.
  • Amylase is naturally produced by the body as part of the digestion process.
  • Without amylase, starch breakdown would take significantly longer.

Common Enzymes: Peptidases

  • Peptidases are a family of enzymes that break down proteins into polypeptides and amino acids.
  • Peptidases catalyze the hydrolysis reaction that breaks peptide bonds.
  • Peptidase 1, found in dust mite feces, is a common allergen.

How Enzymes Decrease Activation Energy

  • Enzymes provide an active site where substrates (reactants) bind.
  • This binding reduces the activation energy by positioning substrates correctly for bond breakage and formation.
  • Bringing substrates closer together accelerates reactions compared to substrates randomly drifting.

Induced Fit

  • Enzymes exhibit specificity, similar to a lock and key.
  • The enzyme's shape changes slightly upon substrate binding to create a better fit, known as induced fit.

Enzyme Substrate Complex

  • The complex formed when substrates bind to the enzyme is called the enzyme/substrate complex.
  • The reaction occurs within this complex, and the products are released.

Another View of Enzyme Function

  1. The active site is available for the substrate.
  2. The substrate binds to the enzyme.
  3. The substrate is converted to products. Example: Sucrose + Sucrase + H2OH_2O -> Glucose + Fructose
  4. Products are released.